Diode fault detection system and method

ABSTRACT

Disclosed are a system and method of detecting a diode fault among diodes coupled to a plurality of redundant power feeds. A diode short fault may be detected by measuring a first voltage across a first one of the diodes, measuring a second voltage between two nodes including a terminal of the first diode and detecting the diode short based upon the first and second voltages. A diode open fault may be detected by decoupling a first one of the diodes from a power feed and measuring the voltage across the diode.

BACKGROUND

[0001] 1. Field

[0002] The subject matter disclosed herein relates to high availabilityprocessing platforms. In particular, the subject matter disclosed hereinrelates to detecting faults in high availability processing platforms.

[0003] 2. Information

[0004] Telecommunication processing and enterprise data centerprocessing systems are typically designed to meet requirements of highavailability of resources. For example, such systems typically compriseredundant resources to meet certain requirements of fault tolerance.Processing resources are typically provided in rack mounted enclosuresto enable convenient servicing or replacement of subsystems. Such rackmounted enclosures also typically comprise front panel displays enablinga system operator to visually observe status indications.

[0005] A high availability platform typically receives redundant powersources such that the platform will not fail if one of the power sourcesfails. Such redundant power sources typically provide a plurality ofpower feeds to components or subsystems through a backplane, baseboardor motherboard.

BRIEF DESCRIPTION OF THE FIGURES

[0006] Non-limiting and non-exhaustive embodiments of the presentinvention will be described with reference to the following figures,wherein like reference numerals refer to like parts throughout thevarious figures unless otherwise specified.

[0007]FIG. 1 shows a diagram illustrating a component chassis adapted toreceive a plurality of redundant power feeds according to an embodimentof the present invention.

[0008]FIG. 2 shows a diagram of a component chassis adapted to receive aplurality of redundant power feeds according to an alternativeembodiment of the present invention.

[0009]FIG. 3 shows a flow diagram illustrating a process to detect adiode short fault according to embodiments of the present invention asillustrated in either FIG. 1 or FIG. 2.

[0010]FIG. 4 shows a flow diagram illustrating a process to detect adiode open fault according to embodiments of the present invention asillustrated in either FIG. 1 or FIG. 2.

DETAILED DESCRIPTION

[0011] Reference throughout this specification to “one embodiment” or“an embodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrase “in one embodiment” or “an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in one or moreembodiments.

[0012] “Machine-readable” instructions as referred to herein relates toexpressions which may be understood by one or more machines forperforming one or more logical operations. For example, machine-readableinstructions may comprise instructions which are interpretable by aprocessor compiler for executing one or more operations on one or moredata objects. However, this is merely an example of machine-readableinstructions and embodiments of the present invention are not limited inthis respect.

[0013] “Machine-readable medium” as referred to herein relates to mediacapable of maintaining expressions which are perceivable by one or moremachines. For example, a machine readable medium may comprise one ormore storage devices for storing machine-readable instructions or data.Such storage devices may comprise storage media such as, for example,optical, magnetic or semiconductor storage media. However, this ismerely an example of a machine-readable medium and embodiments of thepresent invention are not limited in this respect.

[0014] “Logic” as referred to herein relates to structure for performingone or more logical operations. For example, logic may comprisecircuitry which provides one or more output signals based upon one ormore input signals. Such circuitry may comprise a finite state machinewhich receives a digital input and provides a digital output, orcircuitry which provides one or more analog output signals in responseto one or more analog input signals. Such circuitry may be provided inan application specific integrated circuit (ASIC) or field programmablegate array (FPGA). Also, logic may comprise machine-readableinstructions stored in a memory in combination with processing circuitryto execute such machine-readable instructions. However, these are merelyexamples of structure which may provide logic and embodiments of thepresent invention are not limited in this respect.

[0015] A “backplane” as referred to herein relates to a system levelcircuit board that is capable of being coupled to one or more subsystemlevel circuit boards. For example, a backplane may comprise one or moresockets as “backplane interfaces” for integrating subsystem circuitboards or expansion cards with other circuitry disposed on or coupled tothe backplane. However, these are merely examples of a backplane andbackplane interface, and embodiments of the present invention are notlimited in these respects.

[0016] A “plug-in-unit” (PIU) as referred to herein relates to anelectronic subsystem module which is adapted to be plugged into a socketof a larger system. For example, PIU may be adapted to be plugged into abackplane disposed within a component chassis. Such a backplane maytransport power to the PIU and couple the PIU to other subsystems.However, this is merely an example of a PIU and embodiments of thepresent invention are not limited in this respects.

[0017] A “diode” as referred to herein relates to an electronic deviceenabling a forward electrical current to flow from a first terminal to asecond terminal but preventing a reverse electrical current flowing fromthe second terminal to the first terminal. Accordingly, the diode mayact as a “closed circuit” in response to the forward electrical currentand act as an “open circuit” in response to the reverse electricalcurrent. In one embodiment, the physical characteristics and operatingenvironment of diode may prevent (or at least impede) the forwardelectrical current from flowing from the first terminal to the secondterminal until a voltage between the first and second terminals exceedsa threshold “diode turn-on” voltage. However, these are merely examplesof a diode and a diode turn-on voltage, and embodiments of the presentinvention are not limited in these respects.

[0018] In the course of operation, a diode may incur a “diode open”failure or fault characterized by the diode substantially providing anopen circuit in response to current flowing in either direction betweenfirst and second terminals of the diode. A diode may also incur a “diodeshort” failure or fault characterized by the diode substantiallyproviding a short circuit in response to current flowing in eitherdirection between first and second terminals of the diode. However,these are merely examples of a diode open and diode short failures, andembodiments of the present invention are not limited in these respects.

[0019] A “power feed” as referred to herein relates to a source toprovide electrical power to an electronic system. For example, one ormore subsystems disposed within a component chassis may externallyreceive a power feed. Also, a power feed may be coupled to a backplaneto transport the power feed to one or more subsystems coupled to thebackplane. However, these are merely examples of a power feed andembodiments of the present invention are not limited in these respects.

[0020] An electronic system may receive a plurality of “redundant powerfeeds” such that the electronic system is capable of at least partialoperation in an event that one of the redundant power feeds fails.However, this is merely an example of redundant power feeds andembodiments of the present invention are not limited in this respect.

[0021] Briefly, embodiments of the present invention relate to a systemand method of detecting a diode fault among diodes coupled to aplurality of redundant power feeds received at equipment. A diode shortfault may be detected by measuring a first voltage across a first one ofthe diodes, measuring a second voltage between two nodes including aterminal of the first diode and detecting the diode short based upon thefirst and second voltages. A diode open fault may be detected bydecoupling a first one of the diodes from a power feed and measuring thevoltage across the diode. However, these are merely example embodimentsand other embodiments are not limited in these respects.

[0022]FIG. 1 shows a diagram of a component chassis 12 adapted toreceive a plurality of redundant power feeds 14 according to anembodiment of the present invention. The component chassis 12 may houseany one of several types of high availability processing platforms suchas, for example, modular telecommunication processing platforms,enterprise servers, data storage platforms and network data switches.However, these are merely examples of high availability processingplatforms and embodiments of the present invention are not limited inthese respects.

[0023] The component chassis 12 comprises a backplane 18 which isadapted to receive a power entry module (PEM) 16 and one or moreplug-in-units (PIUs) 20. The PEM 16 is adapted to couple the power feeds14 to circuitry on the backplane 18. The PEM 16 may also compriseover-current protection devices such as circuit breakers CB1 and CB2, orfuses F1 and F2 for coupling power from the redundant power feeds 14 tothe backplane 18. The backplane 18 may comprise circuitry to transportpower from the power feeds 14 to the PIUs 20 including, for example,sockets to receive the PEM 16 and PIU 20s, and a printed circuit boardcoupling the sockets with circuit traces. Fuses F and a current rushlimiter 36 may prevent power feed current overloads at the backplane 18during electrical short on the board and during board insertion. Whilethe embodiment of FIG. 1 shows power being provided to one or more PIUs20, it should be understood that in other embodiments redundant powerfeeds may be provided to non-modular equipment (e.g., stand aloneequipment) independently of an intermediary backplane. Also, while theembodiment of FIG. 1 shows two redundant power feeds 14, it should beunderstood that other embodiments may provide three or more redundantpower feeds to a PIU through a backplane or non-modular equipmentdirectly. While the embodiment of FIG. 1 shows that one or more PIUs 20may receive power feeds 14 from a single PEM 16, it should be understoodthat in other embodiments each PIU may receive one or power feeds frommultiple, redundant PEMs such that if a single PEM fails, each PIU maystill receive a power feed from a remaining PEM.

[0024] For each redundant power feed 14, a PIU 20 may comprise acorresponding biased diode 22 coupled to the power feed 14 by a switch26. The diodes 22 are coupled at first terminals to a common node “c.”Each of the diodes 22 comprises a second terminal coupled to a switch 26to selectively couple or decouple the diode 22 from an associated powerfeed 14.

[0025] In the presently illustrated embodiment, each diode 22 may bebiased to permit current to flow from the associated power feed 14 to acorresponding PIU 20 and prevent current from flowing from Feed 2 toFeed 1 of the power feeds 14. Accordingly, the diode 22 actssubstantially as an open circuit in response to current flowing fromFeed 2 to Feed 1, or Feed 1 to Feed 2 of the power feeds 14. A diodefailure or fault may occur in which a diode 22 is short (permittingcurrent to flow between the Feed 1 and Feed 2 of the power feeds 14) oropen (inhibiting current from flowing between the power feed 14 and thecorresponding PIU 20 in either direction). While the diodes 22 are shownbiased to permit current flowing in one direction in the power feed 14,it should be understood that in other embodiments that the diodes 22 maybe biased to permit current to flow in an opposite direction in thepower feeds to support negative feed voltages.

[0026]FIG. 2 shows a diagram of a component chassis 62 adapted toreceive a plurality of redundant power feeds 64 according to analternative embodiment of the present invention. The component chassis62 comprises a PEM 67 which is adapted to receive the redundant powerfeeds 64. A backplane 68 may be adapted to receive one or more PIUs 70.The PEM 67 may comprise over current protection circuitry such ascircuit breakers CB1 and CB2, or fuses F1 and F2 for coupling power fromthe redundant power feeds 64 to the backplane 68. The backplane 68 maycomprise circuitry to transport power from the power feeds 64 to PIUs 70including, for example, sockets to receive the PIUs 20, and a printedcircuit board coupling the sockets with circuit traces. While theembodiment of FIG. 1 shows power being provided to one or more PIUs 70,it should be understood that in other embodiments redundant power feedsmay be provided to non-modular equipment (e.g., stand alone equipment)independently of an intermediary backplane. While the embodiment of FIG.2 shows two redundant power feeds 64, it should be understood that otherembodiments may provide three or more redundant power feeds to a PIUthrough a backplane, or non-modular equipment. While the embodiment ofFIG. 2 shows that one or more PIUs 70 may receive power feeds 64 from asingle PEM 67, it should be understood that in other embodiments eachPIU may receive one or power feeds from multiple, redundant PEMs suchthat if a single PEM fails, each PIU may still receive a power feed froma remaining PEM.

[0027] For each redundant power feed 64, a PIU 70 may comprise acorresponding biased diode 72 coupled to the power feed 64 by a switch76. The diodes 72 are coupled at first terminals to a common node “c.”Each of the diodes 72 comprises a second terminal coupled to a switch 76to selectively couple or decouple the diode 72 from an associated powerfeed 64. In the presently illustrated embodiment, for each power feedreturn 82, a PIU 70 may also comprise a biased diode 73 coupled to eachpower feed return 82 by a switch 77. The diodes 73 are also coupled atfirst terminals to a common node “c.”

[0028] In the presently illustrated embodiment, each diode 72 may bebiased to permit current to flow from the associated power feed 64 to acorresponding PIU 70 and prevent current from flowing from thecorresponding PIU 70 to the power feed 64. Accordingly, the diode 72 mayact substantially as a short circuit in response to current flowing fromthe power feed 64 to the corresponding PIU 70 and may act substantiallyas an open circuit in response to current flowing from the PIU 70 to thepower feed 64. A diode failure or fault may occur in which a diode 72 isshort (permitting current to flow between the power feed 64 and thecorresponding) or open (inhibiting current from flowing between thepower feed 64 and the corresponding PIU 70 in either direction).

[0029] Also, each diode 73 may be biased to permit return current toflow from a corresponding PIU 70 to an associated power feed return 82and prevent current flowing form the power feed return 82 to the PIU 70.Accordingly, the diode 73 may act substantially as a short circuit inresponse to current flowing from the corresponding PIU 70 to the powerfeed return 82 and may act substantially as an open circuit in responseto current flowing from the power feed return 82 to the correspondingPIU 70. A diode failure or fault may occur in which a diode 73 is short(permitting current to flow between the power feed return 82 and thecorresponding PIU 70) or open (inhibiting current from flowing betweenthe power feed return 82 and the corresponding PIU 70 in eitherdirection). While FIG. 2 shows the diodes 72 as being biased to permitcurrent flowing in one direction in the power feeds 64 and the diodes 73as being biased to permit current flowing in another direction in thereturn feeds 82, it should be understood that in other embodiments thatthe diodes 72 and 73 may be biased to permit current to flow in oppositedirections.

[0030] According to the embodiments of either FIG. 1 or FIG. 2, a diodefault detection system (not shown) may be disposed within a chassis(e.g., chassis 12 or 62) to detect diode open or short faults withrespect to one or more of the diodes 22, 72 or 73. Such a diode faultdetection system may be employed as part of a management controllerwhich executes a diagnostic procedure to detect such an open or shortfault, and provide an alert signal to indicate such a condition to allowa system operator to replace a PIU 20 before a failure of the otherredundant diode(s). In response to the alert signal, for example, ashelf manager entity may illuminate a display (e.g., comprising LEDs orLCDs on a rack mounted display) or transmit an external alert signal.However, these are merely examples of how a shelf manager may respond toa diode fault detection alert from a management controller andembodiments of the present invention are not limited in these respects.

[0031] The diode fault detection system may comprise voltage sensors(not shown) coupled to nodes a, b and c, and control circuitry toselectively open or close switches (e.g., switches 26 in FIG. 1, orswitches 76 or 77 in FIG. 2) during the diagnostic procedure. Accordingto an embodiment, the switches 26, 76 or 77 may be electronic switcheswhich may be opened or closed in response to a control signal from thediode fault detection system. Logic in the diode fault detection systemmay comprise any suitable structure for controlling the switches 26, 76or 77 and detecting diode faults from voltage measurements including,for example, a field programmable gate array (FPGA) device, applicationspecific integrated circuit (ASIC) or programmable controller to executemachine-readable instructions from a storage medium. However, these aremerely examples of logic which may provide a diode fault detectionsystem and embodiments of the present invention are not limited in theserespects.

[0032]FIGS. 3 and 4 each illustrate a process to detect a diode fault ina diode labeled “D1” (e.g., a diode 22, 72 or 73 labeled D1). It shouldbe understood, however, that a similar processes may be executed fordetecting a diode short fault in a diode 22 labeled “D2.” Also, in anembodiment, a process to detect diode faults may be executed for eachdiode in response to a diagnostic cycle controlled by a managementcontroller. Accordingly, in response to such a diagnostic cycle,processes to detect a diode short fault or a diode open fault may beexecuted for each diode 22 or 72 coupled to a power feed 14 or 64, oreach diode 73 coupled to a power feed return 82.

[0033]FIG. 3 shows a flow diagram illustrating a process 150 to detect adiode short fault executed by a diode fault detection system accordingto an embodiment of the present invention as illustrated in FIG. 1. Theprocess 150 may be used in identifying diode short faults in diodesamong any pair of diodes D1 and D2 (e.g., a pair of diodes 22, 72 or73). Upon initiation of the process 150 at block 152, the switchescoupled to the diodes D1 and D2 (e.g., switches 26, 76 or 77) are closedand voltages are measured at nodes “a” and “c” to provide voltages V_(a)and V_(c), respectively, indicating a voltage across a diode labeled“D1.”

[0034] If V_(a) and V_(c) are not approximately equal, as indicated atdiamond 154, no diode short fault is detected and the process terminatesat block 164. If V_(a) exceeds a voltage V_(b) measured at node “b” (atdiamond 156) or V_(a) is approximately equal to V_(b) (at diamond 157),then a diode short fault is detected and a short fault detection signalis provided at block 162. Otherwise, the diode fault detection systemmay maintain the switch coupled to diode D1 labeled “S1” in an openstate while re-measuring the voltages V_(a) and V_(c) at nodes “a” and“c” (at block 158). If the re-measured voltages V_(a) and V_(c) areapproximately equal at diamond 160, the diode fault detection systemgenerates a diode fault signal at block 162.

[0035]FIG. 4 shows a flow diagram illustrating a process 200 to detect adiode open fault executed by a diode fault detection system according toan embodiment of the present invention as illustrated in FIG. 1. Theprocess 200 may be used in identifying diode open faults in diodes amongany pair of diodes D1 and D2 (e.g., a pair of diodes 22, 72 or 73). Uponinitiation of the process 200 at block 202, the diode fault detectionsystem may open a switch coupled to diode D2 labeled “S2” and measurevoltages V_(a) and V_(c) at nodes “a” and “c” to determine a voltageacross the diode D1. At diamond 206, if V_(a) exceeds V_(c) by more thana diode turn-on voltage V_(dd) associated with the diode D1, the diodefault detection system generates a diode fault signal at block 208.

[0036] While there has been illustrated and described what are presentlyconsidered to be example embodiments of the present invention, it willbe understood by those skilled in the art that various othermodifications may be made, and equivalents may be substituted, withoutdeparting from the true scope of the invention. Additionally, manymodifications may be made to adapt a particular situation to theteachings of the present invention without departing from the centralinventive concept described herein. Therefore, it is intended that thepresent invention not be limited to the particular embodimentsdisclosed, but that the invention include all embodiments falling withinthe scope of the appended claims.

What is claimed is:
 1. A method of detecting a diode fault comprising:coupling each of a plurality of redundant power feeds to circuitry inequipment through a corresponding one of a plurality of diodes;measuring a first voltage across a first one of said diodes; measuring asecond voltage between two nodes including a terminal of the firstdiode; and detecting a diode short fault based upon the first and secondvoltages.
 2. The method of claim 1, wherein measuring the second voltagefurther comprises: decoupling the first diode from a power feed; andre-measuring the voltage across the first diode.
 3. The method of claim1, wherein measuring the second voltage further comprises measuring avoltage between the first terminal of the first diode and a firstterminal of a second diode, the second diode coupled in parallel to thefirst diode at a common node.
 4. The method of claim 1, the methodfurther comprising decoupling a diode from a power feed; measuring avoltage across the decoupled diode; and detecting a diode open fault inresponse to the measured voltage across the decoupled diode.
 5. Themethod of claim 1, wherein the equipment comprises one or more plug-inunits.
 6. The method of claim 1, wherein the equipment comprisesnon-modular equipment.
 7. A method of detecting a diode faultcomprising: coupling each of a plurality of redundant power feeds tocircuitry in equipment through a corresponding one of a plurality ofdiodes; decoupling the first diode from a power feed; measuring thevoltage across the diode; and detecting a diode open fault based uponthe voltage measured across the diode.
 8. The method of claim 7, whereindetecting a diode open further comprises detecting the diode open inresponse to detecting a voltage difference approximately equal to orgreater than a diode turn-on voltage.
 9. A system comprising: acomponent chassis adapted to receive a plurality of redundant powerfeeds; equipment disposed within the component chassis, the equipmentcomprising a plurality of diodes, each diode coupled to one of saidredundant power feeds; and a diode fault detection subsystem comprising:logic to measure a first voltage across a first one of said diodes;logic to measure a second voltage between two nodes including a terminalof the first diode; and logic to detect a diode short fault based uponthe first and second voltages.
 10. The system of claim 9, wherein thelogic to measure the second voltage further comprises: a switch todecouple the first diode from a power feed; and logic to re-measure thevoltage across the first diode.
 11. The system of claim 9, wherein thelogic to measure the second voltage further comprises logic to measure avoltage between the first terminal of the first diode and a firstterminal of a second diode, the second diode coupled in parallel to thefirst diode at a common node.
 12. The system of claim 9, wherein thediode open detection logic further comprises logic to detect the diodeopen in response to detecting a voltage difference approximately equalto or greater than a diode turn-on voltage.
 13. The system of claim 9,wherein the diode fault detection subsystem further comprises diode opendetection logic including a switch to decouple the first diode from apower feed and logic to measure a voltage across the decoupled diode.14. The system of claim 9, wherein the equipment comprises one or moreplug-in units.
 15. The system of claim 9, wherein the equipmentcomprises non-modular equipment.
 16. A system comprising: a componentchassis adapted to receive a plurality of redundant power feeds;equipment disposed within the component chassis, the equipmentcomprising a plurality of diodes, each diode coupled to one of saidredundant power feeds; and a diode fault detection subsystem comprising:a switch to decouple a diode from a power feed; and logic to measure avoltage across the decoupled diode to detect a diode open fault.
 17. Thesystem of claim 16, diode fault detection logic further including aswitch to decouple the first diode from a power feed and logic tomeasure a voltage across the decoupled diode.
 18. An apparatuscomprising: an interface to a plurality of diodes in a plug-in-unit,each diode coupled to one of a plurality of redundant power feeds; anddiode short detection logic comprising: logic to measure a first voltageacross a first one of said diodes; logic to measure a second voltagebetween two nodes including a terminal of the first diode; and logic todetect the diode short based upon the first and second voltages.
 19. Theapparatus of claim 18, wherein the logic to measure the second voltagefurther comprises: a switch to decouple the first diode from a powerfeed; and logic to re-measure the voltage across the first diode. 20.The apparatus of claim 18, wherein the logic to measure the secondvoltage further comprises logic to measure a voltage between the firstterminal of the first diode and a first terminal of a second diode, thesecond diode coupled in parallel to the first diode at a common node.21. The apparatus of claim 18, wherein the diode open detection logicfurther comprises logic to detect the diode open in response todetecting a voltage difference approximately equal to or greater than adiode turn-on voltage.
 22. The apparatus of claim 18, the apparatusfurther comprising diode open detection logic including a switch todecouple the first diode from a power feed and logic to measure avoltage across the decoupled diode.
 23. The apparatus of claim 18,wherein the equipment comprises one or more plug-in units.
 24. Theapparatus of claim 18, wherein the equipment comprises non-modularequipment.
 25. An apparatus comprising: an interface to a plurality ofdiodes in equipment, each diode coupled to one of a plurality ofredundant power feeds; and diode open detection logic including a switchto decouple the first diode from a power feed and logic to measure avoltage across the decoupled diode.
 26. The apparatus of claim 25,wherein the diode open detection logic further comprises: a switch todecouple the first diode from a power feed; and logic to measure avoltage across the decoupled diode.
 27. An article comprising: amachine-readable medium comprising machine-readable instructions storedthereon to: associate each of a plurality of redundant power feeds witha corresponding one of a plurality of diodes; measure a first voltageacross a first one of said diodes; measure a second voltage between twonodes including a terminal of the first diode; and detect a diode shortfault based upon the first and second voltages.
 28. The article of claim27, wherein machine-readable medium further comprises machine-readableinstructions stored thereon to: initiate a decoupling of the first diodefrom a power feed; and re-measure the voltage across the decoupled firstdiode.
 29. The article of claim 27, wherein machine-readable mediumfurther comprises machine-readable instructions stored thereon tomeasure a voltage between the first terminal of the first diode and afirst terminal of a second diode, the second diode coupled in parallelto the first diode at a common node.
 30. The article of claim 27,wherein the machine-readable medium further comprises machine-readableinstructions stored thereon to: initiate a decoupling of a diode from apower feed; measure a voltage across the decoupled diode; and detect adiode open fault in response to the measured voltage across thedecoupled diode.
 31. An article comprising: a machine-readable mediumcomprising machine-readable instructions stored thereon to: associateeach of a plurality of redundant power feeds with a corresponding one ofa plurality of diodes; initiate a decoupling a diode from a power feed;measure a voltage across the decoupled diode; and detect a diode openfault based upon the voltage measured across the decoupled diode. 32.The article of claim 31, wherein machine-readable medium furthercomprises machine-readable instructions stored thereon to detect a diodeopen fault in response to detecting a voltage difference approximatelyequal to or greater than a diode turn-on voltage.